Role of Nitric Oxide in Optic Nerve Head Blood Flow Regulation During Experimental Increase of Intraocular Pressure in Healthy Humans

Healthy Clinical Trial

Official title:

Role of Nitric Oxide in Optic Nerve Head Blood Flow Regulation During Experimental Increase of Intraocular Pressure in Healthy Humans

Clinical Trial Details — Status: Terminated

Administrative data

• NCT number: NCT00914394
• Other study ID #: OPHT-310708
• Status: Terminated
• Phase: N/A
• First received: June 1, 2009
• Last updated: November 13, 2014
• Start date: October 2010

Study information

• Verified date: November 2014
• Source: Medical University of Vienna
• Contact: n/a
• Is FDA regulated: No
• Health authority: Austria: Agency for Health and Food Safety
• Study type: Interventional

Clinical Trial Summary

Autoregulation is defined as the ability of a vascular bed to adapt its vascular resistance to changes in perfusion pressure. In the eye, several studies have reported that retinal blood flow is autoregulated over a wide range of ocular perfusion pressures. Large scale studies have shown that reduced ocular perfusion pressure is an important risk factor for the prevalence, the incidence and the progression of primary open angle glaucoma.

Former studies that investigated ocular blood flow autoregulation focused mainly on choroidal blood flow. For the optic nerve head only few data are available, although it seems likely that it underlies similar autoregulatory mechanisms.

A previous study investigating choroidal blood flow has shown that nitric oxide (NO) plays a key role in choroidal autoregulation. The present study is designed to test the hypothesis that NO plays a role in optic nerve head autoregulation during increased intraocular pressure (IOP). Therefore, IOP will be experimentally increased using a suction cup device in the absence of presence of either a nitric oxide synthase inhibitor (L-NMMA), an α-receptor agonist (phenylephrine) or placebo. Optic nerve head blood flow will be continuously measured during the procedure.

Recruitment information / eligibility

• Status: Terminated
• Enrollment: 12
• Est. primary completion date: July 2011
• Accepts healthy volunteers: Accepts Healthy Volunteers
• Gender: Both
• Age group: 18 Years to 35 Years

Eligibility

Inclusion Criteria:

• Men and women aged between 18 and 35 years, nonsmokers

• Men and women will be included in equal parts

• Normal findings in the medical history and physical examination unless the investigator considers an abnormality to be clinically irrelevant

• Normal findings in the laboratory testings unless the investigator considers an abnormality to be clinically irrelevant

• Normal ophthalmic findings, ametropia less than 1 diopter

Exclusion Criteria:

• Regular use of medication, abuse of alcoholic beverages, participation in a clinical trial in the 3 weeks preceding the study

• Treatment in the previous 3 weeks with any drug (except intake of oral contraceptives)

• Symptoms of a clinically relevant illness in the 3 weeks before the first study day

• History or presence of gastrointestinal, liver or kidney disease, or other conditions known to interfere with distribution, metabolism or excretion of study drugs

• Blood donation during the previous 3 weeks

• Pregnancy

Study Design

Allocation: Randomized, Endpoint Classification: Safety/Efficacy Study, Intervention Model: Crossover Assignment, Masking: Double Blind (Subject, Investigator, Outcomes Assessor), Primary Purpose: Basic Science

Related Conditions & MeSH terms

• Healthy

Intervention

Drug:
• NG-monomethyl-L-arginine (L-NMMA)
bolus 6mg/kg over 5 minutes followed by a continuous infusion of 60µg/kg/min over 15 minutes
• Phenylephrine
1µg/kg/min, infusion period 20 minutes
• Physiological saline solution (as placebo)
infusion period 20 minutes

Device:
• Laser Doppler Flowmetry
Measurements will be performed at the neuroretinal rim to assess ONH blood flow.
• Goldmann applanation tonometer
intraocular pressure measurements
• Suction cup
Experimental stepwise increase of intraocular pressure while measurement of optic nerve head blood flow.

Locations

Country	Name	City	State
Austria	Department of Clinical Pharmacology, Medical University of Vienna	Vienna

Sponsors (1)

Lead Sponsor	Collaborator
Medical University of Vienna

Country where clinical trial is conducted

Austria, 

Outcome

Type	Measure	Description	Time frame	Safety issue
Primary	optic nerve head pressure-flow relationship		1 year	No